Pentoxifylline

Pentoxifylline (PTX), a tri-substituted purine and xanthine derivative, has been used for several years to improve microcirculation because of its hemorheological properties. PTX has also antifibrotic and anti-inflammatory effects. We studied the reaction of PTX with the hydroxyl radical and superoxide anion. Hydroxyl radical was generated by a mixture of ascorbic acid, H₂O₂ and Fe (III)-EDTA. We evaluated the iron-dependent degradation of deoxyribose, mediated by hydroxyl radical, in the presence of different concentrations of PTX (from 0.05 to 3 mM), measuring the degradation products of deoxyribose that react with 2-thiobarbituric acid (TBA). The reaction of PTX with hydroxyl radical occurred with a rate constant of (1.1±0.2)×10¹⁰ M ⁻¹/s. These results support the properties of PTX as a hydroxyl radical scavenger. Some authors verified that PTX decreases the release of superoxide anion from activated neutrophils. We studied the effect of PTX as a scavenger of superoxide generated in vitro by a hypoxanthine-xanthine oxidase system. PTX was not a superoxide anion scavenger in this system.     

己酮可可碱对肺纤维化大鼠MMP-2和TIMP-1表达的影响

目的观察己酮可可碱(pentoxifylline, PTX)对博来霉素致肺纤维化大鼠肺组织基质金属蛋白酶2(matrix metalloproteinase-2)和基质金属蛋白酶组织抑制剂1(tissue inhibitor of matrix metalloproteinase-1)表达的影响,初步探讨其抗肺纤维化的作用机制.方法 SD大鼠36只,随机分为模型组、治疗组和对照组.模型组和治疗组气管内注射博来霉素诱导肺纤维化,对照组在相同条件下给予生理盐水.第二天起治疗组大鼠腹腔给予己酮可可碱6mg/kg.d,其余两组相同条件下给予生理盐水.治疗的第7d和28d,处死动物取出肺组织,用RT-PCR和免疫组化ABC法观察各组鼠肺组织MMP-2和TIMP-1表达的变化. 结果与模型组比较,治疗组经PTX作用的第7d和28d肺组织中MMP-2和TIMP-1 mRNA的基因转录均有减少,MMP-2 mRNA表达分别降低33.4%和35.5%(P＜0.001),TIMP-1 mRNA表达分别降低25.3%和33.0%(P＜0.05).免疫组化结果则显示,PTX作用的第7d和28dMMP-2分别较模型组降低30.7%和41.7%(P＜0.05),TIMP-1分别降低13.1%和19.8%(P＜0.05).结论 PTX对肺纤维化不同时期肺组织中MMP-2和TIMP-1的表达均有一定程度的降低作用,其可能通过调整MMP-2和TIMP-1比值使其趋于平衡,从而延缓甚至抑制纤维化的进程.     

己酮可可碱对非酒精性脂肪性肝炎大鼠肝脏超微结构和酶组织化学的影响

目的研究己酮可可碱(PTX)对非酒精性脂肪性肝炎(NASH)大鼠肝脏超微结构和酶组织化学的影响。方法高脂饮食建立大鼠非酒精性脂肪性肝炎模型。取SD大鼠40只,分为对照组、12w模型组、16w模型组和治疗组,每组10只。腹主动脉采血,测ALT、AST、血糖等水平。取肝组织做电镜和SDH、CCO、ATPase、LDH的酶组织化学染色。结果两个模型组均比对照组ALT、AST、血糖升高,LDL降低(P<0.05)。治疗组血糖、AST比16w模型组降低(P<0.05)。电镜显示16w模型组线粒体肿大,嵴排列紊乱,基质密度降低。治疗组结构改善。酶组织化学显示四种酶的活性16w模型组均较对照组降低(P<0.05),治疗组活性均较16w模型组升高(P<0.05)。结论NASH时存在肝细胞能量代谢障碍,经PTX治疗后能量代谢障碍得到改善。     

Uterine artery blood flow remains unchanged in pregnant mares in response to short-term administration of pentoxifylline

The objective of this study was to use Doppler ultrasound technology to determine whether pentoxifylline administration increased uterine blood flow in normal pregnant pony mares. Thirteen pregnant pony mares between 18 and 190 d of gestation (mean ± SEM, 101 ± 55) were utilized for the study during two trial periods. In each trial, pentoxifylline (17 mg/kg by mouth every 12h, diluted in syrup) was administered to half of the mares for 3 d, while the other mares were treated with syrup only. Doppler measurements were obtained from the right and left uterine arteries from each mare for 2 d prior to treatment and throughout the treatment period. The mean Resistivity Index (RI), Pulsatility Index (PI), Uterine Artery Diameter (D), and Total Arterial Blood Flow (TABF) from each day were compared over time and between groups. Administration of pentoxifylline did not alter uterine blood flow parameters compared with controls (values for all treatment days combined were RI: 0.517 ± 0.014 vs 0.543 ± 0.016; PI: 0.876 ± 0.048 vs 0.927 ± 0.057; D: 0.388 ± 0.018 vs 0.379 ± 0.023 cm; and TABF: 35.26 ± 7.38 vs 30.73 ± 5.29 mL/min). Uterine blood flow increased over the course of the 5 d study, irrespective of treatment, and was higher in mares of greater gestational age than in early gestational mares (RI: r² = 0.35; PI: r² = 0.37; D: r² = 0.66; and TABF: r² = 0.67 - P < 0.00001). We concluded that any immediate benefits of pentoxifylline administration in the pregnant mare were not mediated through enhanced uterine artery blood flow.     

-Arginine and phosphodiesterase (PDE) inhibitors counteract fibrosis in the Peyronie’s fibrotic plaque and related fibroblast cultures

Inducible nitric oxide synthase (iNOS) is expressed in both the fibrotic plaque of Peyronie's disease (PD) in the human, and in the PD-like plaque elicited by injection of TGFbeta1 into the penile tunica albuginea (TA) of the rat. Long-term inhibition of iNOS activity, presumably by blocking nitric oxide (NO)- and cGMP-mediated effects triggered by iNOS expression, exacerbates tissue fibrosis through an increase in: (a) collagen synthesis, (b) levels of reactive oxygen species (ROS), and (c) the differentiation of fibroblasts into myofibroblasts. We have now investigated whether: (a) phosphodiesterase (PDE) isoforms, that regulate the interplay of cGMP and cAMP pathways, are expressed in both the human and rat TA; and (b) L-arginine, that stimulates NOS activity and hence NO synthesis, and PDE inhibitors, that increase the levels of cGMP and/or cAMP, can inhibit collagen synthesis and induce fibroblast/myofibroblast apoptosis, thus acting as antifibrotic agents. We have found by immunohistochemistry, RT/PCR, and Western blot that PDE5A-3 and PDE4A, B, and D variants are indeed expressed in human and rat normal TA and PD plaque tissue, as well as in their respective fibroblast cultures. As expected, in the PD fibroblast cultures, pentoxifylline (non-specific cAMP-PDE inhibitor) increased cAMP levels without affecting cGMP levels, whereas sildenafil (PDE5A inhibitor) raised cGMP levels. Both agents and L-arginine reduced the expression of collagen I (but not collagen III) and the myofibroblast marker, alpha-smooth muscle actin, as determined by immunocytochemistry and quantitative image analysis. These effects were mimicked by incubation with 8-Br-cGMP, which in addition increased apoptosis, as measured by TUNEL. When L-arginine (2.25 g/kg/day), pentoxifylline (10 mg/kg/day), or sildenafil (10 mg/kg/day) was given individually in the drinking water for 45 days to rats with a PD-like plaque induced by TGF beta1, each treatment resulted in a 80-95% reduction in both plaque size and in the collagen/fibroblast ratio, as determined by Masson trichrome staining. Both sildenafil and pentoxiphylline stimulated fibroblast apoptosis within the TA. Our results support the hypothesis that the increase in NO and/or cGMP/cAMP levels by long-term administration of nitrergic agents or inhibitors of PDE, may be effective in reversing the fibrosis of PD, and more speculatively, other fibrotic conditions.     

Pentoxifylline protects L929 fibroblasts from TNF-alpha toxicity via the induction of heme oxygenase-1

Tumor necrosis factor-alpha (TNF-alpha) is recognized as a principal mediator of a variety of inflammatory conditions. Pentoxifylline (PTX), which can inhibit cellular TNF-alpha synthesis, also attenuates the toxic effect of TNF-alpha. However, the mechanism underlying PTX-induced cytoprotection is unknown. Heme oxygenase 1 (HO-1) is an enzyme which degrades heme into biliverdin, free iron, and carbon monoxide (CO). This enzyme has recently been shown to have anti-inflammatory and cytoprotective effects. In this study, we investigated whether protection by PTX against TNF-alpha-mediated toxicity could be related to its ability to induce HO-1 expression and HO activity in L929 cells. PTX in the range of 0.1-1.0mM significantly induced HO-1 expression and the resulting HO activity. Pre-incubation of L929 cells with either PTX or the HO activator hemin resulted in the protection of the cells against TNF-alpha-mediated toxicity. Zinc protoporphyrin, a specific HO competitive inhibitor, abrogated the protective effect of PTX. Hemoglobin, a scavenger of CO, reversed the protective effect of PTX. A cytoprotection comparable to PTX was observed when the cells were treated with the CO-releasing compound tricarbonyldichlororuthenium(II) dimer. These results suggest that HO-1 expression and the ensuing formation of the HO metabolite CO may be a novel pathway by which PTX protects L929 cells from TNF-alpha-mediated toxicity.     

Effect of pentoxifylline treatment on testicular perfusion and semen quality in Miniature horse stallions

The objective was to investigate the effects of pentoxifylline (PTX) on testicular perfusion and sperm production in stallions. In a preliminary study, six mature Miniature horse stallions were given 0, 8.5, or 17.0 mg/kg of PTX orally, twice daily, for 3 d. Total Arterial Blood Flow Rate (TABFR) was higher (P < 0.05) in all treated versus control stallions during and after treatment. Two months later (during the fall and winter), the same stallions received either 0 or 17 mg/kg of PTX orally, twice daily for 60 d. Resistance and pulsatility indices (RI and PI, respectively) decreased in PTX-treated stallions between Treatment 1 and Post-treatment periods. Arterial diameter, as well as Total Arterial Blood Flow (TABF), decreased in controls between Baseline and Treatment 1 (P < 0.05). A similar decrease in arterial diameter was delayed in Group TREATED, but reached significance during Post-treatment (P < 0.05), whereas TABF did not change in this group. Furthermore, TABFR had a transient tendency to increase during Treatment 1 (P < 0.1), whereas it steadily decreased in controls and reached significance in the Post-treatment period (P < 0.05). Both RI and PI were negatively correlated with end diastolic velocity (EDV) in both groups (P < 0.0001). There were positive correlations between RI and peak systolic velocity (PSV) in treated stallions during Treatment 1 (RI: r = 0.53, P = 0.021; PI: r = 0.59, P = 0.007). Also, there were negative correlations between Time Averaged Maximum Velocity (TAMAX) and Doppler indexes in treated stallions during Treatment 2 period (RI: r = −0.49, P = 0.006; PI: r = −0.47, P = 0.008), and during Post-treatment periods (RI: r = −0.40, P = 0.049; PI: r = −042, P = 0.039). Transient hydrocele occurred in all treated stallions (a potential complication of high-dose PTX). Semen end points were not significantly affected by PTX treatment. In conclusion, PTX delayed the seasonal decrease of testicular perfusion in stallions. Sperm quality and quantity were not significantly affected; perhaps they would have been enhanced by prolonged treatment.     

Influence of immunomodulatory drugs on the cytotoxicity induced by monoclonal antibody 17-1A and interleukin-2

Patients treated with monoclonal antibodies and cytokines for cancer receive often co-medication, which may influence treatment efficacy. Therefore, we investigated with a flowcytometric cytotoxicity assay the effect of several immunomodulatory drugs on antibody dependent cellular cytotoxicity (ADCC), interleukin-2 (IL-2) induced cytotoxicity and IL-2-induced-ADCC. We found that dexamethasone markedly inhibited the IL-2 induced cytotoxicity and the IL-2-induced-ADCC. Ondansetron, a 5-HT-3 serotonin receptor antagonist augmented significantly ADCC. Clemastine, a histamine type-2 receptor antagonist augmented the IL-2-induced-ADCC. The TNF antagonist thalidomide suppressed ADCC whereas pentoxifylline proved to be ineffective. Other tested drugs namely ibuprofen and indomethacin, both prostaglandin E2 antagonists, cimetidine a histamine type-2 receptor antagonist, the opioid pethidine, prostaglandin E2 and histamine exerted minor effects or had no influence on the tested parameters. We conclude that glucocorticosteroids should be avoided with monoclonal antibody and cytokine treatment. According to our in vitro data the other drugs tested did not have a negative impact on cellular cytotoxicity and ADCC.     

Studies on the mechanisms responsible for inhibition of experimental metastasis of B16-F10 murine melanoma by pentoxifylline

Pentoxifylline (PTX), a methylxanthine derivative widely used as a hemorheological agent in the treatment of peripheral vascular disease, was studied to unveil the mechanisms responsible for its inhibitory action on B16-F10 experimental metastasis. In vitro pretreatment of B16-F10 cells with noncytotoxic concentrations of PTX significantly inhibited their adhesion to reconstituted basement membrane Matrigel® and type IV collagen as well as the relative activity of secreted 92 kD metalloproteinase. However, PTX pretreatment of B16-F10 cells did not affect their in vitro invasiveness. Heterotypic organ adhesion assays carried out with B16-F10 cells and suspended organ tissues demonstrated that pretreatment with noncytotoxic concentrations of PTX of both, tumor cells or lung tissue, brought about a dose-dependent inhibition of melanoma cell adhesion to lung. Immunohistochemical studies using antibodies against CD31 adhesion molecule (PECAM-1) revealed that B16-F10 cells adhere to lung endothelial cells. Our results suggest that PTX may exert its inhibitory effect on tumor lodgment, and as a consequence of that on experimental metastases, through an inhibitory action on cell adhesion molecules.